This invention relates to an improved form of non-nutritive, fat-like agents for use in the preparation of low-calorie food compositions. More particularly, this invention relates to dry, microreticulated or microfibrillated microcrystalline cellulose compositions which are readily dispersible in water for use as fat-like substitutes in the preparation of aqueous-based low-calorie foodstuffs. Still more particularly, this invention relates to compositions consisting essentially of agglomerates of microreticulated or microfibrillated cellulose and the hydrocolloids xanthan gum or a carboxymethylcellulose in a dry, particulate form. The resulting composition provides a fat-like consistency, appearance, and mouthfeel when reconstituted as a component in aqueous-based low calorie foods, particularly such foods as salad dressings, dairy products such as frozen desserts, and the like.
By the term xe2x80x9cagglomeratexe2x80x9d, as used herein, is meant a stable, substantially physical mixture of at least two components in its wet or dry state whose components are loosely bound to each other when dried, but disperse into its component parts when reconstituted in water under typical food processing conditions. This physical state is to be distinguished over xe2x80x9caggregatesxe2x80x9d, which are firmly bound components in particle form which remain bonded to each other even if reconstituted in water under typical food processing conditions.
The use of fat-like substitutes in the preparation of low-calorie food compositions is now generally well-established in the art. See, for example, U.S. Pat. No. 5,192,569 (McGinley, et al.), as well as those set forth in the background description of U.S. Pat. No. 5,011,701 (Baer et al.).
More particularly, in that latter patent, i.e. U.S. Pat. No. 5,011,701, there is described a fat substitute material comprising a microreticulated form of microcrystalline cellulose and xanthan gum. As described therein, the term microreticulated microcrystalline cellulose (MRC) defines a highly sheared form of known microcrystalline cellulose (MCC) obtained by shearing an aqueous dispersion of about 3-10 wt. % of MCC under certain defined conditions, reagglomerating the resulting fragments under further high shear conditions to obtain an aqueous dispersion of MRC particles having a void volume of about 25 percent, and a particle size of from about 5-20 microns having a given particle size distribution.
To this aqueous, agglomerated MRC dispersion, according to the description in U.S. Pat. No. 5,011,701, may thereafter be separately added, along with other components, xanthan gum to stabilize the resulting aqueous dispersion which is then directly blended with selected food components to prepare a low fat or fat-free foodstuff.
The aqueous MRC composition which is mixed with xanthan gum and food components, while effective for the purpose intended in preparing low-calorie foodstuffs, nevertheless does not have substantial economic usefulness and flexibility in commerce in view of the need to admix it directly with the food components in the form of its aqueous dispersion as it is made, rather than in a redispersible dry form. That is to say, as will be shown in Example 4 below, attempts to dry the aqueous MRC dispersion by conventional means results in aggregates of material which cannot satisfactorily be redispersed in an aqueous medium for further mixture with food components.
In accordance with the present invention there is now provided an improved food additive composition comprising dry, readily water-dispersible, agglomerates in particulate form, said particles consisting essentially of microreticulated microcrystalline cellulose (MRC) or microfibrillated microcrystalline cellulose (MFC) in a predominant amount by weight and a hydrocolloid selected from xanthan gum and a carboxymethylcellulose (CMC), the hydrocolloid being present in amounts sufficient to provide effective coverage of the MRC or MFC. The invention is directed also to methods of preparing low-calorie food compositions containing the aforesaid compositions, as well as to the food compositions themselves.
The microcrystalline cellulose employed in the preparation of the MRC starting material of this invention should desirably but not necessarily be of colloidal size, i.e., it may have an average particle size of about 0.1-100 microns, depending upon how the MCC is prepared, and preferably a particle size distribution such that not more than about 10-40% of the particles are over about 0.2-0.5 micron size. Particles of this size and distribution are obtained by conventional means, as for example by hydrolysis of the cellulose pulp, followed by wet mechanical disintegration.
The extraction and processing of microcrystalline cellulose from wood pulp or fiber is well known in the art as described, for example, in U.S. Pat. Nos. 3,539,365 and 4,263,334 (above). For purposes of this process, the MCC can be in the form of a mechanically disintegrated aqueous slurry or wetcake having a solids content ranging from about 5 to 45% by weight, depending upon whether a high solids attrition is employed, e.g. about 30-45% solids, or a low solids, i.e. wet solids milling process (e.g. about 5-10% solids) known to the art is employed. See, for example, O. A. Battista, xe2x80x9cMicrocrystalline Polymer Sciencexe2x80x9d, pp. 39, 40, McGraw-Hill Book Co., (1975), and U.S. Pat. No. 2,978,446. The preparation of MCC is also described in FMC Corporation Bulletins L-0786 AAPS (1986) and G-34 (1985). As described therein, microcrystalline cellulose wetcake obtained from wood pulp which has been hydrolyzed with acid in a known manner may be simply spray-dried to produce a non-colloidal, powered grade of cellulose (Avicel xe2x80x9cPHxe2x80x9d grade Cellulose, e.g., PH 101) or mechanically disintegrated to form a colloidal grade of cellulose (Avicel xe2x80x9cRC/CLxe2x80x9d grade cellulose, both available from FMC Corporation, Philadelphia, Pa.). Depending upon how the cellulose wetcake is treated, if at all, the particle size of these various grades may range from about 0.1 to about 10 microns for the colloidal grade, and from about 10 to 100 microns for the non-colloidal grades. It will be understood that these ranges, which may overlap somewhat, will determine the size of the resulting MCC.
The microreticulated form of microcrystalline cellulose employed herein may then be prepared from MCC in accordance with the examples below, as well as by the high shear methods described in U.S. Pat. No. 5,011,701 (above), which, again, is incorporated by reference, particularly the description in columns 5 and 6 thereof.
Alternatively there may be employed as the microcrystalline cellulose component of the composition claimed herein the microfibrillated microcrystalline cellulose (MFC) of U.S. Pat. No. 4,378,381 (Turbak et al.), or related patents, U.S. Pat. No. 4,374,702; U.S. Pat. No. 4,483,7343; or U.S. Pat. No. 4,452,721, all of which are incorporated herein by reference, and which describe a fibrillated cellulose which is also prepared from microcrystalline cellulose. This cellulose, (MFC), which is defined as having increased surface area, greater liquid absorption characteristics, and greater reactivity, is prepared, according to these patents, by passing a liquid suspension of fibrous cellulose through a small diameter orifice in which the suspension is subjected to a pressure drop of at least 3000 psi and a high velocity shearing action followed by a high velocity decelerating impact and repeating the passage of said suspension through the orifice until the cellulose suspension becomes a substantially stable suspension. The process converts the cellulose into microfibrillated cellulose without substantial chemical change. The resulting MFC is characterized in having a water retention value of over 280%, a settling volume after 60 minutes in a 0.5% by weight suspension in water of greater than 60% and a rate of degradation increase by hydrolysis at 60xc2x0 C. in one molar hydrochloric acid at least twice as great as cellulose beaten to a Canadian Standard Freeness value of 50.
The resulting MFC, in aqueous suspension form, may then be used in this invention in place of, or in addition to, the microreticulated cellulose described above in U.S. Pat. No. 5,011,701.
Thus, as used hereinafter throughout this description, the term xe2x80x9cmicroreticulated crystalline cellulosexe2x80x9d shall also be understood to include the aforesaid xe2x80x9cmicrofibrillated microcrystalline cellulosexe2x80x9d in the novel compositions of this invention.
Following the conversion of the MCC to its MRC form, which is porous, the hydrocolloid, which must be xanthan gum or CMC since not all hydrocolloids are effective for this purpose, is then added to the aqueous dispersion in amounts sufficient to effectively penetrate the reagglomerated cellulose pores, and thus coat the individual cellulose particles by adsorption. Alternatively, the hydrocolloid may be added to the MCC prior to its conversion to the MRC form; this is conveniently achieved by hydrating the xanthan gum to form an aqueous solution which may then be admixed vigorously with the MCC. In either case, it is essential that the two materials be admixed to form hydrocolloid-coated particles of MRC (or MFC) before the composition is dried. By the term xe2x80x9ceffectively coatxe2x80x9d, as used above, is meant coating the MRC sufficiently to permit its ready redispersion in water, for example under aqueous food-mixing conditions, in contrast to an inadequate coating which would allow the cellulose to become irreversibly aggregated.
The mixing of these two components may be accomplished by the use of high shear equipment such as Waring blenders, colloid mills, homogenizers, and the like. The solids content of this mixture is not critical and may be varied routinely, depending upon the consistency needed for the subsequent drying step. In a typical procedure, the mixing is carried out until the desired size agglomerate of the two components is obtained in the form of a slurry, generally at room temperature. Following this the slurry may, if necessary, be further sheared, as for example in a homogenizer, to obtain a uniform and homogeneous distribution of the components, just prior to the drying step.
The resulting mixture must then be co-dried by spray drying, to form the composition of this invention, namely an agglomerate in powder form whose particles are readily dispersible in water. As used herein, the term xe2x80x9cdryxe2x80x9d includes powdered agglomerate which may contain up to a few percent of water which has been absorbed by the cellulose and/or hydrocolloid.
Because the MRC comprises a predominant amount by weight of the resulting composition, the weight ratio of hydrocolloid to MRC should desirably be about 0.08-0.33:1.0, and preferably about 0.14-0.18:1.0, although these ratios are not critical.
The effectiveness of the redispersibility of the composition of this invention under the high shear conditions of food processing, for example, can be seen from the viscosity properties of the aqueous dispersion prepared from the powdered product obtained by the spray-drying. That is to say, the viscosity of the rehydrated powder of this invention is about the same as the viscosity of the slurry before spray-drying. Thus, while the viscosity of any given preparation will depend upon the nature of its ingredients, that viscosity is, surprisingly, maintained both before and after spray-drying.
The particle size of the MRC or MFC in the resulting dispersion should be desirably be in the range of from about 10 to 40 microns, and preferably about 3 to 15 microns, particularly if it is to be used as a fat-like substitute. In order to assure this particle size distribution, spray drying conditions may be regulated in a known manner, i.e. conditions which influence particle size and size distribution, including the method of atomization (nozzle, centrifugal types), rate of atomization (wheel speed, nozzle size, nozzle atomizing air pressure and the like), and slurry properties such as viscosity and its related solids content. For instance, the more dilute the slurry the smaller the resulting particle size and the narrower the particle size distribution. Those skilled in the art will also recognize that by varying the particle size distribution, in particular by adjusting the nozzle size, and/or the pressure at which the homogenized slurry to be dried is pumped through the nozzle, the desired particle size will be obtained. The operating temperatures can be regulated by selecting optimal operating inlet and outlet temperatures. It will be recognized that these temperatures are not critical and can be varied substantially depending upon the properties of the slurry to be dried.
The compositions of this invention are readily incorporated in the desired foodstuffs, such as salad dressings or dairy products, by various means. In general, it is preferred to disperse the particulate composition in water to form an aqueous dispersion, which is then processed with the foodstuffs by conventional food processing, i.e., mixing, means.
The amount of the aqueous MRC-hydrocolloid-containing dispersion which may be incorporated in a given foodstuff is not critical and can be varied considerably. Generally, the amount of dispersion employed should be sufficient to provide the foodstuff with the desired fat-like characteristics, including mouthfeel, bulk, consistency and the like. Thus, foodstuffs may contain as little as about 0.5% of the agglomerate solids content, based on the total weight of the food composition, or as much as about 5%, and desirably about 1-3%. For example, salad dressings may desirably contain from about 1.5 to 3% of agglomerate in the final formulation, while dairy products such as frozen desserts may contain from about 0.5 to 2.0% of the agglomerate.
Other foodstuffs which may advantageously be improved by this invention include candies, frostings, gravies, margarines, mayonnaise, meat and vegetable fillings, puddings, sauces, soups, spreads, and like water-based foods.